my 08 f250 king ranch has been at the dealership 4 times in the last two months because the ac continues to go out. Complete dash removal twice. Found a leak on one shredder valve... Changed it. Also replaced the evaporator . They charged it the last time, it was parked for a week and I started it up and no ac. Took it back to ford and they said there was no freon. They removed the dash again, put dye in and can't find a leak. Any clues?

 

Take a UV flashlight, and park in a dark garage, (dye will glow blue) and look over every part of the AC system (pump, accumulator, condenser, lines, and what you can see of the evaporator). If it is leaking that fast you should see the dye somewhere.

Also, there is an AC forum on here and those guys really know their stuff. They helped me alot when I replaced my whole AC system (pump, condenser, accumulator, and flushed the lines and evaporator) on my 06 F250 when the accumulator material contaminated the whole AC system.